Buying an used watch/vintage, the seller can not write the date of purchase on the warranty card.
So a birthday purchase or an other special date notation (wedding) is lost.
This what i go to write is not investigated, when new watches sold, more watches go into the world, and it keeps on work for companies like factories, stores, designers.
Tax incomes.
Personally i like the way a new watch is crisp, clean, undamaged. Like a new born. A new time.